Electric motor.



L. F. JOHNSON.

ELECTRIC MOTOR.

APPLICATION IILED'SBPT. 22, 1904.

Patented Apr. 20, 1909.

- 2 SHEETS-SHEET 1.

L. P. JOHNSON.

BLEOTRIO morron.

APPLICATION FILED SEPT. 22, 1904. 9 1 8,86 1. Patented Apr. 20, 1909.

2 SHEETSSHEET 2 hurrah STA'Il LOUIS F. JOHNSON, OF CHICAGO, ILLINOIS,ASSIGNOR, BY MESNE ASSIGNMENTS, TO P. 8: O. ELECTRIC CO., A CORPORATIONOF ARIZONA TERRITORY.

ELECTRIC MOTOR.

Application filed September 22, 1904.

To all whom it may concern:

Be it known that I, LOUIS F. JOHNSON, a citizen of the United States ofAmerica, and a resident of Chicago, in the county of Cook and State ofIllinois, have invented certain new and useful Improvements in ElectricMotors, of which the following is specification.

The main objects of my invention are to provide an electric motorcapable of being controlled and reversed by a simple movement of thebrushes, to provide suitable means for preventing short circuiting ofthe armature of an electric motor by moisture; to provide in the windingof electric motors one or more secondary or auxiliary paths of highresistance adapted to take up an ercessive flow of current due toshifting of the brushes out of their normal position, sudden changes ofthe load or sudden reversals of the current; to provide improvedarrangement of the material of the field magnets to obtain a combinationwhich will readily saturate with magnetism, and while demagnetizingquickly under reversals of the current, will, when the brushes areturned to the neutral position, retain a large quantity of residualmagnetism and tend to cause the motor to operate as a generator, thusforming resistance for quickly stopping the rotation of the armature;and to provide suitable grounding of the iield windings and the armaturewind: ings to the framework of the motor so as to cause a part of thecurrent to be deflected and flow through the framework, setting upinduced currents serving as scattered internal resistance antagonisticto the normal How of current through the windings, whenever suchwindings are subjected to a sudden rush of current endangering theinsulation thereof. I accomplish these objects by the device shown inthe accompanying drawings, in which:

Figure l is a diagrammatic view of a motor constructed according to myinvention. Fig. 2 is a side elevation of the armature and brush holder,showing a choke coil in circuit therewith and omitting the field magnetsand certain other parts of the supporting frame. Fig. 3 is adiagrammatic view show ing the method of connecting the choke coil. Fig.l is a detail view showing the construction of the brush holder.

In the form shown in the drawings, the hold magnet consists of a pair ofmassive Specification of Letters Patent.

Patented April 20, 1909.

Serial No. 225,449.

pole pieces 1 and 2 opposed to each other, and connected together bymeans of cylindrical cores 3. The field magnet is rigidly secured to asuitable base, which is not shown in the drawing, and to which are alsosecured the bearings 4 and 5 for the armature shaft 6. The armature isof the Gramme ring type, comprising an annular core 7 consisting oflaminated rings of annealed. iron bound together and rigidly secured tothe shaft 6 by means of a suitable spider not shown in the drawing. Anyform of winding which is suitable for motors of this type may be used.In the particular form shown, the field coils S and 9 are connected inseries with the armature winding 9, which consists of a series ofadjacent coils connected together and having their junctions connectedwith the bars of the commutator 10 in the usual way.

One of the field coils is grounded on the core of the held at G a pointnear the junction of such coil with the line. One of the convolutions ofthe armature circuit is also grounded in a similar manner at G byconnected with the core of the armature. These connections between thewindings and their cores are preferably made by means of shortconductors of high resistance. In small motors a needle driven throughthe copper wire and into the core has proven to be a good connection forthis purpose. This grounding of the windings forms an auxiliary path ofhigh resistance, normally deflecting only a slight portion of thecurrent; but in cases where the winding is subjected to excessive flowof current, the windings become heated somewhat causingtheir resistanceto become more nearly equal to that of the said auxiliary path, whichthen deflects a larger proportion of the current and thus assists thewindings in taking careof such excessive flow and prevents them frombecoming short circuited and burned out through failure of theirinsulation.

The brushes 11 are mounted on a brush holder 12 which is journaled onsleeve 13 surrounding the shaft 6 and secured to the bearing 5. Thebrush holder 12 is adapted to be rotated through an angle of more than180 degrees around the sleeve 13 and is provided with a handle 21 whichis threaded into the holder 12 and adapted to be screwed into and out ofengagement with the sleeve 13 for securing the brush holder 12 in afixed posi being tion. This shifting of the brush holder 12 per mits thebrushes to be moved from a neutral position relatively of the poles 1and 2 to different angular positions in either direction from suchneutral position, thereby varying the number of magnetic lines of forceout by each branch of the armature circuit and consequently increasingor decreasing the speed of the motor. It will be seen that setting thebrushes at one side of the neutral point will cause the armature torotate in a certain direction, while if the brushes are turned to theopposite side of the neutral point, the direction of flow of the currentthrough the ar mature coils, will be reversed without reversing thedirection of the flow of current through the field coils, causing thearmature to rotate in the opposite direction.

W hen using current of high voltage, I supplement the grounding of thearmature and field windings with a choke coil 14 which is shown mountedon the sleeve 13 and is so connected with the brushes as to be broughtinto and out of the armature circuit when the brushes are moved out ofor into their neutral position. 'When the brushes are in their neutralposition, the resistance of the choke coil serves to diminish theexcessive flow of current in the armature circuit. As shown in Fig. 2two annular conductors 15 and 16 are secured to the sleeve 13 near thebrush holder 12. The conductors 15 and 16 are insulated from the sleeveand from each other and are adapted to be engaged by a brush or finger17 on the brush holder. The finger 17 is electrically connected with oneof the brushes 1 1. One end of the choke coil is connected to theconductor 16, while its other end is connected by the wire 18 to one ofthe field coils 8. he conductor 15 is connected directly to said fieldcoil 8 by the wire 19. It will be seen that when the finger 1'7 is incontact with the conductor 15, the choke coil 14 will not be in circuit;and when the finger 17 engages the conductor 16, the choke coil 14 willbe brought into the circuit and will serve through its resistance toreduce the fiow of current through the armature. The conductors 15 and16 are so arranged that the conductor 15 will be engaged by the finger17 when the brushes are in the neutral position, while the conductor 16will be engaged by the finger 17 when the brushes are in positions awayfrom the neutral position, thus avoiding an excessive rush of currentthrough the armature circuit and preventing sparking when the brushesare out of their neutral position.

The cores are constructed of soft annealed iron which will readilysaturate with magnetism and at the same time quickly become demagnetizedwhen the current is changed. The pole pieces 1 and 2, on the contrary,are constructed of the cheapest grade of cast iron which is hard andretains a considerable amount of residual magnetism after the current iscut oil". serves to resist the rotation of the armature when the currentis shut oil and the motor is thus quickly brought to a standstill.

In operation, the motor is connected with the line by a switch which isnot shown in the drawings. The speed and direction of rotation of thearmature are all controlled by setting the brushes through the movementof the handle 21, thus accomplishing the control by varying thedirection of the current in the armature coils relatively of the polesof the field.

Other features of the operation of the device shown will be readilyunderstood from the foregoing description.

It will be understood that numerous details of the construction shownmay be altered without departing from the spirit of my invention, and itwill also be understood that my invention may be applied to other typesof motor or windings of other character.

What I claim as my invention and desire to secure by Letters Patent, is:

1. In a device of the class described, the combination of an iron core,an insulated conductor wound on said core for magnetizing the same, andsuitable conductors of relatively high resistance connecting the core asshunt of its windings for deflecting a portion of the current when thewindings are heated by an excessive current, substantially as described.

2. A motor having field cores and an armature core in el ctricalconnection with each other, a field winding grounded on tile fieldmagnet, and an armature winding grounded on the armature core,substantially as and for the purpose specified.

3. In a motor, the combination of a field magnet, an armature core,windings on said field magnet and said armature core, a conductor ofhigh resistance connecting the field winding to the field magnet, and aconductor of hi 'h resistance connecting the armature winding and thearmature core, substantially as described.

Signed at Chicago this 20th day of September, 1904.

LOUIS F. JOHNSON.

Witnesses EUGENE A. RUMMLER, GLEN O. STEPHENS.

This residual magnetism

